Belt grinder with cam-controlled tensioning means

ABSTRACT

A driving pulley is rotatably mounted in a frame in contact with an endless driving belt and is power operable to drive the same. A roller is adapted to contact the belt. A tensioning finger carried by the frame carries the roller and extends inside the belt between the pulley and roller. Cam means carried by said frame is operatively arranged to engage the finger and move the roller for adjusting tension in the belt.

United States Patent 1111 4,

[72] Inventor Hans Georg Wezel 1,913,574 6/1933 Vicic l/170.4 P.0. Box 60, 7533 Maulbronn (Wuer 2,232,149 2/1941 Tautz 51/135 Hemberg), Germany 2,260,949 10/1941 Mall 1. 51/170.4 [21] Appl. No. 818.939 2,740,238 4/1956 Sharpless 51/148 122] Filed Apr. 24, 1969 3,049,841 8/1962 Guinn 51/170.4 Patemad July 197] Primary Examjner-William R. Armstrong Att0rneyPolachek & Saulsbury [54] BELT GRINDER WITH CAM-CONTROLLED TENSIONING MEANS 7 Claims, 5 Drawing Figs.

[52] U.S.Cl ..5l/lEB, 51/148 [51] h t. Cl ..B24b 23/00 ABSTRACT; A driving puney is rotatably mounted in a fr Field of Search 51/1704, in contact with an endless driving belt and is power operable 135, v 148, 170 to drive the same. A roller is adapted to contact the belt. A tensioning finger carried by the frame carries the roller and [56] References cued extends inside the belt between the pulley and roller. Cam UNITED STATES PATENTS means carried by said frame is operatively arranged to engage 1,108,176 8/1914 Hormel 51/148 the finger and move the roller for adjusting tension in the belt.

7 P' P u 7 -fLi /s 4 LEI 7 l l 1 x1 40 4 PATENTED JUL 2 1 |97i SHEET 2 BF 3 Weze/ BELT GRINDER WITH CAM-CONTROLLED I TENSIONING MEANS This invention relates to an improvement in a belt grinder, which comprises a frame carrying a driving pulley. A grinding belt extends from the driving pulley and is held taut and in contact with a roller by a tensioning finger.

In operations involving high pressure, the resilient tensioning of the revolving grinding belt may cause the latter tojump off the rollers. This will be avoided by the present improvement, in which a tensioning finger extending between the pulley and a roller is also used so that the grinding belt can be contacted by a workpiece on all sides.

The belt grinder according to the invention comprises a grinding belt, which extends from a driving pulley and is held taut and in contact with a roller by a tensioning linger. 'Ihe tensioning finger extends between the pulley and a roller and within the grinding belt. The finger can be moved into and out of its tensioning position by a control means comprising a slidable wedge or a rotatablecam. This will enable an adjustment of the tension of the grinding belt and this adjusted tension will not be decreased when the working pressure is reduced so that a satisfactory condition of the belt is ensured in any case. To that end, the tensioning finger extending from the driving pulley may be guided in a passage in a frame member containing the control means comprising the wedge or cam. The frame member is pivotally and detachably mounted on a hub ofthe frame below the driving pulley.

Further details of the belt grinder according to the invention will now be explained with reference to the drawing, in which FIGS. 1 and 2 are, respectively, a side elevation and a top plan view, partly in section, showing a belt grinder according to the invention;

FIGS. 3 and 4 are elevations showing different types of tensioning fingers; and

FIG. 5 is a partly sectional view showing another tensioning device.

As is apparent from FIGS. 1 and 2 of the drawings, a drive unit 40 is accommodated in the handle 1. An angle gearing 2 in frame 42 drives a cross-shaft 3, which carries a driving pul' ley 4 for the grinding belt 5. The drive unit 40 may consist of a compressed-air motor, an electric motor or a driven flexible shaft. In the first embodiment, the grinding belt 5 extends around the roller 6 at the distal end 7 of a finger 7. This finger has a straight proximal end 7 engaged in a passage 10 formed in a frame member 9. Frame member 9 is pivotally mounted on a hub 11 of frame 42 and can be locked in place by a radial bolt 46 on the hub. The hub is coaxial with pulley 4 and is located below the driving pulley. It is larger in diameter than the driving pulley so that it can be removed from the frame without disturbing the pulley. C-shapcd removable collar 12 holds the frame member 9 on hub 11. The finger 7 and roller 6 are wholly confined in the space between the two spaced planes P and P defined by opposite edges of the endless belt. A cam 8 having a curved peripheral face 8' is eccentrically and rotatably mounted by a pin 44 in a cavity in frame member 9. The curved face of the cam contacts the proximal end of finger 7 in this cavity and bears against it. The cam can be rotated to move finger 7 in a direction parallel to planes P, P so that roller 6 bears against an inside loop of belt 5 to exert tension thereon. An adjustment screw 8a is supported by frame member 9 and is disposed axially parallel to the pulley and roller. This screw bears against the curved face of cam 8 at a point of contact with finger 7 to adjust the cam and to hold the cam in any selected position of adjustment, so that the roller is held in contact with the belt tensioning the same. It will be noted that the finger and roller support for the belt is substantially symmetrical about a central plane P midway between planes P, P. This insures balance of the belt during a grinding operation. It will be further noted that the cam 8 exerts pressure on finger 7 in central plane P. This eliminates the skewing and binding encountered with prior belt-tensioning devices applying tension nonsymmetrically with respect to opposite edges of the belt. A finger guard 11a extends around the driving pulley 4. The tensioning finger 7, which is adjustable by the angular position of 'cam 8 extends entirely within the grinding belt 5 so that the working part of the latter is exposed on all sides. The tensioning roller 6 at the end of the tensioning finger is laterally adjustable about the pin 13 by a screw 14 against the action of the spring 15 so that the proper course of the belt can be adjusted so as to prevent a lateral slipping of the belt. I

Further embodiments of replaceable tensioning fingers are shown in FIGS. 3 and 4. FIG. 3 shows tensioning finger 16 with opposite end portions 16, 16" disposed at an obtuse angle to each other. Grinding belt 17 extends around the driving pulley I8 and is supported by a deflecting roller 19 and an end roller 20. In this case too the tensioning finger is adjustable by a control cam 21 and the end roller 20 is pivotally movable in a lateral direction at 22. FIG. 4 shows a tensioning finger 23 having opposite end portions 23', 23 disposed perpendicular to each other. Grinding belt 24 extends around a driving pulley 25, a deflecting roller 26, and an end roller 27. A control cam is indicated at 28 and the lateral pivotal movement of the end roller 27 at 29.

FIG. 5 shows a slide track member 32 which comprises a control wedge 30 for the tensioning finger 31 rather than a control cam as shown in the preceding embodiments. The wedge 30 is adjusted by an adjusting screw 33, which is held by a collar 34. The end of. the tensioning finger is engaged in dovetail groove 35 formed in the wedge 30.

What I claim is:

l. A belt grinder, comprising a frame; an endless grinding belt; a power-driven driving pulley rotatably mounted on said frame in contact with said belt to drive the belt; a roller disposed axially parallel to said pulley rotatably engaging said belt so that the belt is supported while being driven in the direction of its length, opposite edges of said belt defining two parallel spaced planes; a tensioning finger for the belt carried by said frame, said finger having distal and proximal end portions, said finger rotatably supporting the roller at the distal end of the finger, said finger and roller being wholly confined in the space between said planes sothat the entire outside surface of the belt is exposed for grinding, said frame having a passage formed therein axially parallel to the two planes defined by opposite edges of the belt, the axis of said passage lying-in a central plane midway betweensaid two planes, said proximal portion of the finger being slidably disposed in said passage to move in a direction perpendicular to the axes of the pulley and roller for adjustably holding the roller in contact with the belt; cam means movably carried by the frame and bearing on the proximal end of the finger to tension the belt, said cam means being adjustably positionable to move the finger in said direction so that the belt is adjustably tensioned by pressure of the roller carried by the finger while the belt is symmetrically supported and tensioned with respect to said central plane and so that skewing and binding of the belt as it is being driven in prevented; and screw means carried by the frame and extending axially parallel to the pulley and roller, said screw means engaging the cam means to adjust and hold the same in any selected position of adjustment so that tension in said belt is maintained.

2. A belt grinder as defined in claim 1, wherein said cam means is a cam having an eccentric axis of rotation; means rotatably supporting said cam in the frame, said cam having a curved peripheral cam face engaging said proximal end of said finger, said screw means bearing against said cam face at a point spaced eircumferentially from proximal end of said finger and offset laterally from its eccentric axis of rotation.

3. A belt grinder as defined in claim 1, wherein said cam means is wedge-shaped with an inclined face bearing against said proximal end of said finger.

4. A belt grinder as defined in claim 1, wherein both end portions of said finger are straight and axially aligned with each other.

5. A belt grinder as defined in claim 1, wherein both end has a hub formed thereon axially parallel to said pulley; a portions of said finger are straight and angularly inclined to frame member pivotally mounted on said hub, said frame I each other. member containing said passage and supporting said cam 6. A belt grinder as defined in claim 1, wherein both end means, and a bolt carried y said frame mcmberand engaging portions f Said finger are straight and perpendicmar to each 5 said hub to lock the frame member in different selected posiother. tions circumferentially of said hub.

7. A belt grinder as defined in claim 1, wherein said frame 

1. A belt grinder, comprising a frame; an endless grinding belt; a power-driven driving pulley rotatably mounted on said frame in contact with said belt to drive the belt; a roller disposed axially parallel to said pulley rotatably engaging said belt so that the belt is supported while being driven in the direction of its length, opposite edges of said belt defining two parallel spaced planes; a tensioning finger for the belt carried by said frame, said finger having distal and proximal end portions, said finger rotatably supporting the roller at the distal end of the finger, said finger and roller being wholly confined in the space between said planes so that the entire outside surface of the belt is exposed for grinding, said frame having a passage formed therein axially parallel to the two planes defined by opposite edges of the belt, the axis of said passage lying in a central plane midway between said two planes, said proximal portion of the finger being slidably disposed in said passage to move in a direction perpendicular to the axes of the pulley and roller for adjustably holding the roller in contact wiTh the belt; cam means movably carried by the frame and bearing on the proximal end of the finger to tension the belt, said cam means being adjustably positionable to move the finger in said direction so that the belt is adjustably tensioned by pressure of the roller carried by the finger while the belt is symmetrically supported and tensioned with respect to said central plane and so that skewing and binding of the belt as it is being driven in prevented; and screw means carried by the frame and extending axially parallel to the pulley and roller, said screw means engaging the cam means to adjust and hold the same in any selected position of adjustment so that tension in said belt is maintained.
 2. A belt grinder as defined in claim 1, wherein said cam means is a cam having an eccentric axis of rotation; means rotatably supporting said cam in the frame, said cam having a curved peripheral cam face engaging said proximal end of said finger, said screw means bearing against said cam face at a point spaced circumferentially from proximal end of said finger and offset laterally from its eccentric axis of rotation.
 3. A belt grinder as defined in claim 1, wherein said cam means is wedge-shaped with an inclined face bearing against said proximal end of said finger.
 4. A belt grinder as defined in claim 1, wherein both end portions of said finger are straight and axially aligned with each other.
 5. A belt grinder as defined in claim 1, wherein both end portions of said finger are straight and angularly inclined to each other.
 6. A belt grinder as defined in claim 1, wherein both end portions of said finger are straight and perpendicular to each other.
 7. A belt grinder as defined in claim 1, wherein said frame has a hub formed thereon axially parallel to said pulley; a frame member pivotally mounted on said hub, said frame member containing said passage and supporting said cam means, and a bolt carried by said frame member and engaging said hub to lock the frame member in different selected positions circumferentially of said hub. 